In the prior art radar operators were often trained on radar equipment and a target aircraft would be flown on a predetermined path while performing predetermined maneuvers within the operational range of the radar. This type of training is very costly due to the high cost of operating aircraft, and such training must be scheduled in advance. Due to these factors and the difficulty of scheduling more than one aircraft at a time for radar operator training, multiple target training has been extremely limited and is usually obtained only when the radar operator is working with real lift situations such as near an airport. When emergency situations arise involving multiple aircraft, and possibly under adverse operating conditions for both the radar equipment and the aircraft, lack of multiple target training for the radar operator can result in the increase of the changes of an air accident that might otherwise be avoided if a more experienced operator had been operating the radar equipment. Further, live aircraft maneuvering is often not repeatable enough when evaluating radar operators or competing radar systems and displays.
As a result of the shortcomings of radar operator training utilizing actual aircraft as detailed above, equipment has been developed to generate simulated radar target return signals that are input to the radar equipment to display the nonexistent training aircraft on the radar plan position indicator for training and testing purposes. In addition, multiple aircraft can be more easily simulated. Such equipment for generating simulated target returns also eliminates the scheduling problems of using real aircraft for training and the attendant cost thereof. Further, this simulated radar display equipment can be utilized at any time of the day or night at any location where there is radar equipment or even simply a PPI console. Live targets, where available, are easily intermixed with the simulated targets.
There are shortcomings, however, in the prior art simulated radar display equipment resulting in a lack of simulated target reality, except in very complex simulation systems using large real time on line computers. This prior equipment does not provide terrain masking simulation, nor does the equipment provide for multiple target displays due to target causing range gate splitting, nor does this prior art equipment provide manual or automatic ambiguity checking. In addition, the prior art simulated radar display equipment does not provide variable target size to simulate coincident targets, different size targets and turning targets presenting varying physical profile to the radar beam. Further, the prior art simulated radar display equipment does not provide simulation of antenna drive motor speed variations caused by wind loading, and does not provide simulated displays reflecting different antenna rotational speeds.
In the prior art, generation of simulated multiple target displays required relatively extensive use of a large computer with the attendant operating and programming costs thereof. The computer is used to generate a target trajectory and each target trajectory is then further processed by the computer to be in the signal format required to be input to the simulated display equipment and then to the radar display equipment. When it is desired to change the trajectory of a target the computer must repeat the generation of the trajectory and the conversion of the trajectory to either polar or rectangular coordinates at appropriate time intervals.
From the above it is apparent that there is a need in the art for improved simulated radar target display equipment that will generate signals to display realistic target scenarios to radar operators for training purposes. In addition, there is a need for simulated radar target display equipment that can easily change target trajectories without the need for an expensive dedicated computer. Such equipment should be inexpensive, small and lightweight to permit its wide usage.